On varieties of MV-algebras with internal states

In [4,5] the authors introduced the variety SMV of MV-algebras with an internal operator, state MV-algebras. In [2,3] the authors gave a stronger version of state MV-algebras, called state-morphism MV-algebras. In this paper we continue the studies presented in [2,3] just looking at several proper subvarieties of SMV, obtained by imposing suitable conditions on the behavior of the internal operator.